Pressure vessels are used in many technical fields. They are usually made of metal and pressurized by a gaseous or liquid medium. In typical applications, pressure vessels of this type are employed to supply a liquid substance, such as a liquid adhesive, by means of pressurized air from a container placed in the pressure vessel via a supply line to a location where the adhesive or other liquid is used.
A typical prior-art pressure vessel is disclosed in German Patent specification 3,116,961. This known vessel is intended for use with drainage systems of laundry installations. It has a flange at its upper periphery in which a sealing ring completely surrounding the vessel opening is inserted. The vessel is closed by a pressure cover having a lower flange. The flanges of both the vessel body and the cover are penetrated by eighteen threaded bolts equally spaced along the periphery. A uniform closing pressure is intended to be achieved by tightening the bolts.
Opening and closing the known pressure vessel is time consuming as it requires all bolts to be individually and manually operated. Further, in practice, the individual bolts will be tightened with different torques, which will cause distortions of the cover, possibly even leaks.
Austrian Patent specification 298,427 describes a pressure vessel which comprises a vessel body, a cover and a sealing including a sealing ring sealingly connected to the inner peripheral wall of the cover and an annular element connected to the outer peripheral wall of the vessel body and cooperating with the sealing ring. The sealing ring has an area which is situated radially outwardly of the line of engagement between the sealing ring and the annular element and exposed to the pressure inside the vessel. Further provided is a bayonet-type locking for securing the cover to the vessel body in a first non-sealed position and in a second, sealed closing position.
The pressure inside the vessel is used to create the sealing force by virtue of the pressure difference which acts on the annular surface portion of the sealing ring outside the line of engagement referred to above. The bayonet locking further permits easy and rapid opening and closing of the vessel. Since the pressure supply is disconnected when the vessel is opened or closed, the cover may be placed on, and removed from, the vessel body without effort. The first, non-sealed position of the cover is provided to ensure a gradual pressure reduction when the vessel is opened.